This invention relates generally to gas turbine engines, and more specifically to gas turbine engine assemblies and methods of assembling the same.
At least some known gas turbine engines include a fan assembly, a core engine, and a low-pressure or power turbine. The core engine includes at least one compressor, a combustor, and a high-pressure turbine that are coupled together in a serial flow relationship. Air entering the core engine is mixed with fuel and ignited to form a high energy gas stream. The high energy gas stream flows through the high-pressure turbine to rotatably drive the high-pressure turbine and thus the compressor via a first drive shaft. The gas stream expands as it flows through the high-pressure turbine to facilitate driving the low-pressure turbine which rotatably drives the fan assembly through a second drive shaft.
To improve engine efficiency, it is desirable to operate the fan assembly at a relatively low speed to improve fan efficiency and to operate the high-pressure turbine at a relatively high speed to improve turbine efficiency. Accordingly, neither the fan speed nor the high-pressure turbine speed may be totally optimized to improve overall engine efficiency.
As such, at least one known gas turbine engine includes a gearbox coupled between the low-pressure turbine and the fan assembly to facilitate reducing the operational speed of the fan assembly. However, utilizing a gearbox to reduce the speed of the fan assembly and thus increase the efficiency of the fan assembly reduces the quantity of airflow channeled to the booster compressor. As a result, additional stages may be added to the booster compressor to achieve proper pressure, thus increasing the overall weight, design complexity and/or manufacturing costs of such an engine.